OpenMP: Support 'if (simd:/cancel:' in Fortran

OpenMP: Support 'if (simd:/cancel:' in Fortran

gcc/fortran/ChangeLog:

	* gfortran.h (enum gfc_omp_if_kind): Add OMP_IF_CANCEL and OMP_IF_SIMD.
	* openmp.c (OMP_SIMD_CLAUSES): Add OMP_CLAUSE_IF.
	(gfc_match_omp_clauses, resolve_omp_clauses): Handle 'if (simd/cancel:'.
	* dump-parse-tree.c (show_omp_clauses): Likewise.
	* trans-openmp.c (gfc_trans_omp_clauses, gfc_trans_omp_cancel,
	(gfc_split_omp_clauses): Likewise.

gcc/testsuite/ChangeLog:

	* gfortran.dg/gomp/cancel-2.f90: New test.
	* gfortran.dg/gomp/cancel-3.f90: New test.
	* gfortran.dg/gomp/if-1.f90: New test.